PGT
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Understanding Preimplantation Genetic Testing
a. Purpose and Objective: PGT involves the genetic analysis of embryos created through in vitro fertilization (IVF) to identify any genetic abnormalities or chromosomal disorders before their transfer into the uterus.
b. Types of PGT: There are three main types of PGT:
i. PGT-A (Aneuploidy screening): This form of PGT screens for chromosomal abnormalities, such as aneuploidy (abnormal number of chromosomes). It helps identify embryos with the correct number of chromosomes, increasing the chances of implantation and reducing the risk of miscarriage.
ii. PGT-M (Monogenic/single gene disorder testing): PGT-M is used to identify specific genetic mutations or inherited disorders carried by the parents. It allows for the selection of unaffected embryos, reducing the risk of passing on genetic diseases to the child.
iii. PGT-SR (Structural rearrangement testing): PGT-SR is performed when one or both parents have structural rearrangements in their chromosomes. It helps identify embryos with balanced chromosomal arrangements, minimizing the risk of miscarriage or developmental issues.
The Process of PGT
a. IVF and Embryo Development: PGT is typically performed in conjunction with IVF. After ovarian stimulation and egg retrieval, fertilization occurs in the laboratory, resulting in the development of embryos.
b. Biopsy: On day 5 or 6 of embryo development, a small number of cells are safely and minimally removed from each embryo for genetic analysis. This biopsy does not harm the embryo’s potential for implantation.
c. Genetic Analysis: The extracted cells are then analyzed using various advanced techniques, such as polymerase chain reaction (PCR), fluorescence in situ hybridization (FISH), or next-generation sequencing (NGS), depending on the specific type of PGT.
d. Embryo Selection: Based on the genetic analysis, embryos without abnormalities or carrying the desired genetic traits are selected for transfer into the uterus.
Advantages of Preimplantation Genetic Testing
a. Increased Pregnancy Rates: PGT-A helps identify chromosomally normal embryos, improving the chances of successful implantation and reducing the risk of miscarriage.
b. Reduction of Genetic Disorders: PGT-M enables the selection of embryos without specific genetic mutations, reducing the risk of passing on inherited disorders to the child.
c. Emotional Relief: PGT provides individuals and couples with valuable information about the genetic health of their embryos, offering peace of mind and alleviating anxieties related to potential genetic disorders.
Considerations and Limitations
a. Accuracy: PGT is highly accurate but not 100% foolproof. There is a small chance of misdiagnosis or mosaicism (when an embryo has a mix of normal and abnormal cells).
b. Ethical Considerations: PGT raises ethical concerns, such as the potential for selecting embryos based on non-medical traits or the creation and subsequent discarding of embryos.
c. Cost and Accessibility: PGT can be an additional expense to IVF treatment, and its availability may vary depending on the country or fertility clinic.
Conclusion
Preimplantation Genetic Testing (PGT) has revolutionized the field of assisted reproductive technologies, offering individuals and couples enhanced opportunities for a successful pregnancy. By identifying chromosomally normal embryos and screening for specific genetic disorders, PGT increases the chances of achieving a healthy pregnancy and reduces the risk of passing on genetic abnormalities to future generations.